Complete Mitogenome of Cruznema tripartitum Confirms Highly Conserved Gene Arrangement within Family Rhabditidae

Abstract

Mitochondrial genomes have widely been used as molecular markers in understanding the patterns and processes of nematode evolution. The species in genus Cruznema are free-living bacterivores as well as parasites of crickets and mollusks. The complete mitochondrial genome of C. tripartitum was determined through high-throughput sequencing as the first sequenced representative of the genus Cruznema. The genome is comprised of 14,067 bp nucleotides, and includes 12 protein-coding, two rRNA, and 22 tRNA genes. Phylogenetic analyses based on amino acid data support C. tripartitum as a sister to the clade containing Caenorhabditis elegans and Oscheius chongmingensis. The analysis of gene arrangement suggested that C. tripartitum shares the same gene order with O. chongmingensis, Litoditis marina, Diplocapter coronatus, genus Caenorhabditis, and Pristionchus pacificus. Thus, the mitochondrial gene arrangement is highly conserved in the family Rhabditidae as well as some species in Diplogasteridae.

Transcriptomics of Cruznema velatum (Nematoda: Rhabditidae) with a redescription of the species

“…Using the identical nematode culture of Du et al . (2022), our detailed morphological study rejects previous identification as C. tripartitum and redescribes it as C. velatum. This misidentification emphasises the difficulty in distinguishing closely related nematode species, even among taxonomists.…”

“…More recently, the mitogenome of C. tripartitum was sequenced, and the phylogeny placed this species as sister to the clade containing C. elegans and Oscheius chongmingensis (Du et al 2022). Using the identical nematode culture of Du et al (2022), our detailed morphological study rejects previous identification as C. tripartitum and redescribes it as C. velatum. This misidentification emphasises the difficulty in distinguishing closely related nematode species, even among taxonomists.…”

“…Based on the 18S, 28S, and ITS of rRNA sequences, our phylogenetic analysis support the genus Cruznema as monophyetic, in line with a previous study (van Megen 2009). More recently, the mitogenome of C. tripartitum was sequenced, and the phylogeny placed this species as sister to the clade containing C. elegans and Oscheius chongmingensis (Du et al 2022). Using the identical nematode culture of Du et al .…”

“…The species belonging to the genus Cruznema are free-living bacterivores that contribute to nitrogen mineralization by consumption of bacteria and excretion of excess nitrogen (Ferris et al 1997). Phylogenetically, this genus is closely related to C. elegans (Du et al 2022). In respect to soil ecology, they play a major role in the cave's food web, which can be an indication of soil quality (Lau et al 1997).…”

“…In this study, a population of genus Cruznema Artigas, 1927, which was initially identified as C. tripartitum (Du et al 2022), was characterised as C. velatum Brzeski, 1989 by morphological and molecular data. Biological characters including generation time, reproduction type, and fecundity were also studied.…”